Since man first began keeping animals in confining enclosures, problems have been enountered in assuring that adequate water is available. Troughs have been used in conjunction with livestock, and in more recent times, various float valve systems have been devised to maintain a constant water level in such troughs. These systems have generally been elaborate, permanent installations that are relatively expensive to install and maintain.
For smaller enclosures for one or two animals such as dog pens where relatively small amounts of water are consumed, a permanent watering system cannot be economically justified. Thus, the old-fashioned method of placing a bowl of water in the pen, which is periodically refilled, is today the method almost universally used for watering dogs and similar animals. The major drawback of this method, of course, is that the water must be checked at least every other day and should be inspected daily in case the animal has turned the bowl over. This requirement for confined care is not only time consuming but is confining to the owner or attendant.